1) Place the ruler on the table with about 3 inches
hanging over the end.

2) Place the two sheets of newsprint over the ruler,
keeping it in the middle, and smooth them so that there is no air between
them and the table top.

3) Hit the end of the ruler hard. If you hit it hard
enough, the ruler will break.

Explanation: By smoothing the
paper, you pushed most of the air out from under it, but there is still a lot
of pressure from the air above it. When you hit the stick, it breaks because
it can not rise up in response to the force you used on it, the air pressure
above is too high.